Texture and Flavor Improvement of Aged Indica Rice by Integrated Ultrasonication‐Assisted Infrared Cooking via Starch Structures and Water Status Modification

The ultrasonication-assisted infrared cooking (USIC) on the improvement of texture and flavor of aged Indica rice was evaluated, and the role of ultrasonication was discussed considering starch structures and water status modifications, with varying ultrasonic powers (400-1000 W). Results showed that the moisture content in cooked and stir-fried aged Indica rice was increased, the hydrogen bond freedom and the proportion of immobile water were enhanced by USIC. The amylose content was reduced from 23.17 ± 0.06 g/100 g to 18.04 ± 0.17-19.91 ± 0.13 g/100 g, the relative crystallinity of rice starch declined from 18.32% to 3.32%-4.82%. FTIR spectrum analysis indicated the R_{1047/1022 cm} ^-1 achieved a lower value (1.08-1.09), starch-protein interactions were weakened, starch-lipid complex formation was aggravated. USIC increased rapidly digested starch (RDS) content but decreased slowly digested starch (SDS) and resistant starch (RS) content. At ultrasonic powers ≥ 800 W, RS content was elevated. The hardness, chewiness, and stickiness of both USIC cooked and stir-fried rice were reduced; however, it presented a firstly decreasing and then increasing trend with the ultrasound power, with the lowest value achieved with the ultrasonic power 600 W. Microstructurally, USIC-treated rice exhibited a sponge-like porous structure with a rougher surface and fissured cross-section. USIC had no negative effect on the oil oxidation of stir-fried rice; the prominent flavor of aged Indica rice from sulfides and nitrogen oxides after cooking was attenuated and balanced by electronic nose analysis. It indicated USIC can serve as a novel approach to enhance the sensory quality of aged rice products.